CFD study on thermal transport in open-cell metal foams with and without a washcoat: Effective thermal conductivity and gas-solid interfacial heat transfer

publisher: Elsevier articletitle: CFD study on thermal transport in open-cell metal foams with and without a washcoat: Effective thermal conductivity and gas-solid interfacial heat transfer journaltitle: Chemical Engineering Science articlelink: http://dx.doi.org/10.1016/j.ces.2016.12.006 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.publisher: Elsevier articletitle: CFD study on thermal transport in open-cell metal foams with and without a washcoat: Effective thermal conductivity and gas-solid interfacial heat transfer journaltitle: Chemical Engineering Science articlelink: http://dx.doi.org/10.1016/j.ces.2016.12.006 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.publisher: Elsevier articletitle: CFD study on thermal transport in open-cell metal foams with and without a washcoat: Effective thermal conductivity and gas-solid interfacial heat transfer journaltitle: Chemical Engineering Science articlelink: http://dx.doi.org/10.1016/j.ces.2016.12.006 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.This work was supported by the National Natural Science Foundation of China (No. 51276181, 21306192) and the National Key Research and Development Program – China (2016YFB0601203)

An experimental study of flow and heat transfer of supercritical carbon dioxide in multi-port mini channels under cooling conditions

This paper presents the fluid flow and heat transfer characteristics of supercritical CO2 in a horizontal multi-port extruded aluminum test section consisting of 10 circular channels with an inner diameter of 1.31 mm. Both local and average pressure drop and heat transfer coefficients were measured as CO2 was cooled in the multi-port circular channels with pressures ranging from 7.4 to 8.5 MPa, inlet fluid temperatures ranging from 22 to 53°C, and mass velocity ranging from 113.7 to 418.6 kg/m2 s. The results indicate that the operating pressure, the mass velocity and the temperature of CO2 had significant effects on fluid flow and heat transfer characteristics. The pressure drop and the average heat transfer coefficient increased greatly with increasing the average temperatures of CO2 in the near-critical region; the average heat transfer coefficient attained a peak value near the corresponding pseudocritical temperature; and the maximum heat transfer coefficient decreased as the pressure increased. Both the pressure drop and the heat transfer coefficient increased with the mass velocity, but decreased with the operating pressure. The measured average heat transfer coefficients were compared with the experimental data reported in the literatures and a large discrepancy was observed. Based on the experimental data collected in the present work, a new correlation was developed for forced convection of supercritical CO2 in horizontal multi-port mini channels under cooling conditions. © 2005 Elsevier Ltd. All rights reserved

Experimental and Numerical Studies of a Recuperator in Micro Turbines

In this paper, a recuperator model is established to simulate the real working state of the recuperator in the micro turbine. The relative error between simulated and experimental data doesn't exceed 5%, which indicates that the model can better reflect the changing law of the recuperator performance. Therefore, the recuperator model proposed in this paper is reasonable and reliable. In addition, the simulation results indicate that heat transfer efficiency is not sensitive to the change of hot inlet temperature, however, it increases with the decrease of mass flow rate. On the other hand, the decrease of inlet mass flow leads to the relative pressure loss decreased on hot and cold sides

IMECE2008-66850 AN ANALYTICAL SOLUTION TO THE THERMAL STRESS AND THERMAL STRAIN IN A CYLINDRICAL LASER ROD WITH LONGITUDINAL TEMPERATURE RISE

ABSTRACT In this paper, a mathematical model of the thermal stress and thermal strain in the laser medium was presented. An analytical solution was further derived for the thermal stress and thermal strain in the laser rod through the method of Thermoelastic Displacement Potential and the method of Love Displacement Function. The analytical solution results show that under the traction free boundary conditions, the longitudinal rise of fluid temperature has little effect on the thermal stress profile in the laser rod. However, the thermal strain field caused by both the temperature and the thermal stress fields has an evident variation in the longitudinal direction, which will affect the laser transmission characteristics and the beam quality

Numerical investigation on multi-stage swirl cooling at mid-chord region of gas turbine blades

Compared with the single-stage one, the multi-stage swirl cooling technique has great potential at the mid-chord region of gas turbine blades. Currently, the effect of the chamber structure at the mid-chord region of the blades on the multi-stage swirl cooling is still unknown. In this study, four kinds of the multi-stage swirl chamber models are built: Case 1 has two swirl nozzles and three chambers, and cases 2-4 have six swirl nozzles and seven chambers. Fluid flow and heat transfer characteristics of the coolant in the swirl cooling configurations are numerically investigated. The standard k-epsilon turbulent model is adopted in current study and the Reynolds number of the coolant varies from 12,000 to 52000. The results show that the long swirl chamber in case 1 has negative effect on the performance of the swirl cooling this is because the swirl velocity along the axial direction is gradually reduced and the Nusselt number is decreased remarkably. For cases 2-4, the chambers are separated into several short ones. Therefore, the swirl velocity could keep high value and so is the Nusselt number. Although more swirl chambers could lead to higher pressure loss coefficient, cases 2-4 show better comprehensive thermal performance as compared to case 1. Among the current cases, the swirl chamber structure in case 4 shows the highest cooling effectiveness and obtains more uniform temperature distributions on the external surface of the blade